Halloween Approximately - S2-E2
Other mistake: In the scene where boys are loading eggs into their slingshots, one of the eggs misses and falls on the roof, but doesn't break. A real egg would have broken.
Halloween Approximately - S2-E2
Continuity mistake: When Francis walks into the boy's room the calendar says September 2000. In the next shot it changes to October 2000. After that Reece says "No, it really is the 31st" he flips up the September page of the calendar to October. (00:06:15 - 00:07:15)
Answer: Francis is only allowed to talk on the phone at school for three minutes a day. I think the code gives him free access to talk to his girlfriend.